Photodynamic therapy mediated by a red LED and methylene blue inactivates resistant Leishmania amazonensis

Cutaneous leishmaniasis is a neglected parasitic disease that leads to destructive lesions. The emergence of drug resistance has been a global concern over the past years. Photodynamic therapy (PDT) mediated by a red LED and methylene blue (MB) involves the overproduction of oxidative stress, which oxidizes several cellular biomolecules and prevents the selection of resistant strains. Herein, we investigated the potential of PDT mediated by MB against wild-type and miltefosine-resistant strains of Leishmania amazonensis. As a result, both strains were susceptible to PDT, thus encouraging us to seek the best conditions to overcome the drug resistance problem in cutaneous leishmaniasis.

Near Infrared-Activatable Methylene Blue Polypeptide Codelivery of the NO Prodrug via π-π Stacking for Cascade Reactive Oxygen Species Amplification-Mediated Photodynamic Therapy

The application of photodynamic therapy (PDT) has attracted remarkable interest in cancer treatment because of the advantages of noninvasiveness and spatiotemporal selectivity. However, the PDT efficiency is considerably limited by photosensitizer (PS) quenching and severe hypoxia in solid tumors. Herein, a kind of near infrared (NIR)-activatable methylene blue (MB) peptide nanocarrier was developed for codelivery of nitric oxide (NO) prodrug JSK, expecting a cascade of reactive oxygen species (ROS) amplification-mediated antitumor PDT. In detail, MB was conjugated to water-soluble polyethylene glycol-polylysine (PEG-PLL) through NIR-photocleavable 10-N-carbamoyl bonds, and the subsequent amphiphilic conjugates (mPEG-PLL-MB) self-assembled into nanoparticles (NPs), which allowed JSK codelivery via π-π stacking interactions. MB in quenched state in mPEG-PLL-MB/JSK NPs could be photoactivated by NIR light locoregionally in a controlled manner due to the photocleavage of carbamoyl bonds. Apart from ROS production, assembly disturbance and even disintegration of mPEG-PLL-MB/JSK occurred along with MB activation that subsequently freed JSK, which was further triggered by intracellularly overexpressed glutathione (GSH) and glutathione S-transferase (GST) to sustain the release of NO. NO then served as a hypoxia relief agent through inhibition of cellular respiration to economize O₂, cooperating with MB activation and GSH depletion, which synergistically enabled a cascade of ROS amplification to augment PDT for mitochondrial apoptosis-mediated tumor inhibition in vitro and in vivo. Therefore, this pioneering strategy of cascade amplification of ROS addressed the key issues of PS inactivation, hypoxia resistance, and ROS neutralization in a three-pronged approach, which hold great promise in efficient antitumor PDT.

Early adjunctive methylene blue in patients with septic shock: a randomized controlled trial

PURPOSE

Methylene blue (MB) has been tested as a rescue therapy for patients with refractory septic shock. However, there is a lack of evidence on MB as an adjuvant therapy, its' optimal timing, dosing and safety profile. We aimed to assess whether early adjunctive MB can reduce time to vasopressor discontinuation in patients with septic shock.

METHODS

In this single-center randomized controlled trial, we assigned patients with septic shock according to Sepsis-3 criteria to MB or placebo. Primary outcome was time to vasopressor discontinuation at 28 days. Secondary outcomes included vasopressor-free days at 28 days, days on mechanical ventilator, length of stay in ICU and hospital, and mortality at 28 days.

RESULTS

Among 91 randomized patients, forty-five were assigned to MB and 46 to placebo. The MB group had a shorter time to vasopressor discontinuation (69 h [IQR 59-83] vs 94 h [IQR 74-141]; p < 0.001), one more day of vasopressor-free days at day 28 (p = 0.008), a shorter ICU length of stay by 1.5 days (p = 0.039) and shorter hospital length of stay by 2.7 days (p = 0.027) compared to patients in the control group. Days on mechanical ventilator and mortality were similar. There were no serious adverse effects related to MB administration.

CONCLUSION

In patients with septic shock, MB initiated within 24 h reduced time to vasopressor discontinuation and increased vasopressor-free days at 28 days. It also reduced length of stay in ICU and hospital without adverse effects. Our study supports further research regarding MB in larger randomized clinical trials. Trial registration ClinicalTrials.gov registration number NCT04446871 , June 25, 2020, retrospectively registered.

Mitochondrial dysfunction mediates neuronal cell response to DMMB photodynamic therapy

Photodynamic therapy (PDT) is a process in which a photosensitizer (PS) is exposed to specific wavelengths and generates reactive oxygen species (ROS) which act within nanometers. The low invasive nature and directed cytotoxicity of this approach render it attractive to the treatment of different conditions, including the ones that affect the central nervous system (CNS). The effect of PDT on healthy neurons is one main concern over its use in the CNS, since neuronal-like cells were shown to be particularly sensitive to certain PSs. Among available PSs, 1,9-dimethyl-methylene blue (DMMB) stands out as being resistant to reduction to its inactive leuco form and by being able to produce high levels of singlet‑oxygen. In this study, we aimed to investigate DMMB photodamage mechanisms in the hippocampal cell line HT22. Our results demonstrate that DMMB-PDT decrease in cell viability was linked with an increase in cell death and overall ROS production. Besides, it resulted in a significant increase in mitochondrial ROS production and decreased mitochondria membrane potential. Furthermore, DMMB-PDT significantly increased the presence of acidic autolysosomes, which was accompanied by an increase in ATG1 and ATG8 homologue GaBarap1 expression, and decreased DRAM1 expression. Taken together our results indicated that mitochondrial and autophagic dysfunction underlie DMMB-PDT cytotoxicity in neuronal cells.

Effect of methylene blue on hemodynamic response in the early phase of septic shock: A case series

RATIONALE

Methylene blue (MB) has been used to increase blood pressure in septic shock, acting on the activity of guanylate cyclase and nitric oxide synthase.

PATIENCE CONCERNS

The aim of this study is to demonstrate the benefit of MB in early phase of septic shock.Diagnoses: We report 6 cases of patients with septic shock with up to 72 hours of evolution.

INTERVENTIONS

We used MB after fluid replacement, use of norepinephrine and vasopressin. Patients received a loading dose of MB and maintenance for 48 hours.

OUTCOMES

All patients presented a reduction in the dose of vasopressors and lactate levels soon after the administration of the loading dose of MB, an effect that was maintained with the maintenance dose for 48 hours. Interleukin 6 and interleukin 8 were elevated at the beginning of the septic condition, with a progressive and marked reduction after the beginning of MB infusion, demonstrating a role of MB in reducing the inflammatory activity.

LESSONS

This case series suggests that MB used early in the treatment of septic shock may be useful in reducing vasopressor dose and lactate levels. Further studies are still required to further validate these findings.

On the Photo-Eradication of Methicillin-Resistant Staphylococcus aureus Biofilm Using Methylene Blue

This work compared the effectiveness of several Methylene Blue (MB)-based protocols for photo-eradication of biofilms formed on the surface of the glass and stainless steel discs by S. aureus MRSA isolates using a diode laser (λ = 665 nm; output power 40 mW; energy fluence was 189 J cm^-2). The results obtained showed that MB alone, up to a concentration of 62.5 mgL^-1, had limited photo-bactericidal activity. It was possible to enhance the activity of MB using two types of spherical gold nanoparticles of similar sizes, 15 ± 3 nm/20 ± 3 nm, but differing in the method of their synthesis and stabilization. The enhancement of the photodestruction effect was related to the increased production of hydroxyl radicals by the MB+gold nanoparticles mixture, and this mixture showed dark cytotoxicity against the cocci studied. Effective destruction (mortality above 99.9%) of the biofilms formed by MRSA isolates was also possible without the use of gold nanoparticles, but the concentration of MB had to be at least 125 mgL^-1. A highly efficient protocol of photodestruction of biofilms, consisting of triple exposure of biofilms to laser light in the presence of MB alone, combined with the removal of dead bacteria protecting deep layers of pathogens against photosensitization, was also described.

Necroptosis activation is associated with greater methylene blue-photodynamic therapy-induced cytotoxicity in human pancreatic ductal adenocarcinoma cells

Pancreatic ductal adenocarcinomas (PDAC) are the fourth leading cause of death due to neoplasms. In view of the urgent need of effective treatments for PDAC, photodynamic therapy (PDT) appears as a promising alternative. However, its efficacy against PDAC and the mechanisms involved in cell death induction remain unclear. In this study, we set out to evaluate PDT's cytotoxicity using methylene blue (MB) as a photosensitizer (PS) (MB-PDT) and to evaluate the contribution of necroptosis in its effect in human PDAC cells. Our results demonstrated that MB-PDT induced significant death of different human PDAC models presenting two different susceptibility profiles. This effect was independent of MB uptake or its subcellular localization. We found that the ability of triggering necroptosis was determinant to increase the treatment efficiency. Analysis of single cell RNA-seq data from normal and neoplastic human pancreatic tissues showed that specific necroptosis proteins RIPK1, RIPK3 and MLKL presented significant higher expression levels in cells displaying a transformed phenotype providing further support to the use of approaches that activate necroptosis, like MB-PDT, as useful adjunct to surgery of PDAC to tackle the problem of microscopic residual disease as well as to minimize the chance of local and metastatic recurrence.

Application of methylene blue combined with ropivacaine intercostal nerve block in postoperative analgesia of autologous costal cartilage augmentation rhinoplasty

OBJECTIVE

To observe the effect of methylene blue combined with ropivacaine intercostal nerve block on postoperative analgesia after autologous costal cartilage augmentation rhinoplasty.

METHODS

In this study 100 female patients who underwent autologous costal cartilage comprehensive augmentation rhinoplasty in Chongqing Huamei Plastic Surgery Hospital from April to November 2021 were randomly divided into an experimental group and a control group, with 50 cases in each group. In the experimental group methylene blue was combined with ropivacaine intercostal nerve block as patient controlled intravenous analgesia (PCIA), and the control group was ropivacaine intercostal nerve block combined with PCIA. The visual analogue scale (VAS) scores of resting and coughing at 6 h (T1), 24 h (T2), 48 h (T3), 72 h (T4) after surgery were recorded and evaluated. At the same time, the number and times of oral analgesics were recorded as well as nausea, vomiting, burning pain and paresthesia.

RESULTS

The VAS scores of the experimental group were lower than those of the control group at all time points. At 6 h, 24 h and 48 h after surgery, the VAS score of the experimental group was lower than that in the control group, but the difference was not statistically significant (P > 0.05). The VAS score of calm 72 h after surgery in the experimental group was significantly lower than that in the control group (P < 0.05). The analgesic effect of the two groups was better when they coughed after surgery. At 6 h after surgery, the VAS score of coughing in the experimental group was lower than that in the control group, but the difference was not statistically significant (P > 0.05); At 24 h, 48 h and 72 h after surgery, the VAS score of the coughing state in the experimental group was significantly lower than that in the control group (P < 0.05).

CONCLUSION

Intercostal nerve block with methylene blue combined with ropivacaine can achieve good postoperative analgesic effects in augmentation rhinoplasty with autologous costal cartilage.

Engineered Mesoporous Silica-Based Core-Shell Nanoarchitectures for Synergistic Chemo-Photodynamic Therapies

Combinatorial therapies have garnered enormous interest from researchers in efficiently devastating malignant tumors through synergistic effects. To explore the combinatorial approach, multiple therapeutic agents are typically loaded in the delivery vehicles, controlling their release profiles and executing subsequent therapeutic purposes. Herein, we report the fabrication of core (silica)-shell (mesoporous silica nanoparticles, MSNs) architectures to deliver methylene blue (MB) and cupric doxorubicin (Dox) as model drugs for synergistic photodynamic therapy (PDT), chemotherapy, and chemodynamic therapy (CDT). MB, as the photosensitizer, is initially loaded and stabilized in the silica core for efficient singlet oxygen generation under light irradiation towards PDT. The most outside shell with imidazole silane-modified MSNs is immobilized with a chemotherapeutic agent of Dox molecules through the metal (Copper, Cu)-ligand coordination interactions, achieving the pH-sensitive release and triggering the production of intracellular hydrogen peroxide and subsequent Fenton-like reaction-assisted Cu-catalyzed free radicals for CDT. Further, the designed architectures are systematically characterized using various physicochemical characterization techniques and demonstrate the potent anti-cancer efficacy against skin melanoma. Together our results demonstrated that the MSNs-based core-shell nanoarchitectures have great potential as an effective strategy in synergistically ablating cancer through chemo-, chemodynamic, and photodynamic therapies.

Dramatic destruction of methicillin-resistant Staphylococcus aureus infections with a simple combination of amoxicillin and light-activated methylene blue

BACKGROUND

Staphylococcus aureus is and continues to be a leading cause of bacterial infections throughout the world. Given the global dissemination of multi-drug resistant (MDR) S. aureus, particularly methicillin-resistant S. aureus (MRSA), novel solutions against S. aureus infections are urgently needed. In our study on the interactions between commonly used photosensitizers and antibiotics in the clinic, we discovered that MRSA can be dramatically destroyed by a simple combination of amoxicillin and light-activated methylene blue (MB).

METHODS

To guide the clinical application of this combination therapy, we quantitatively assessed the interaction between light-activated MB and amoxicillin against S. aureus and its treatment order, dosage, and time length dependence. Furthermore, we evaluated the efficacy of this combination therapy in treating and halting the progression of MRSA infections with the catheter biofilm infection model and the pig skin burn infection model. In the end, we disclosed the antimicrobial mechanisms of this combination therapy to further facilitate its clinical translation.

RESULTS

Amoxicillin and light-activated MB can mutually boost each other's uptake in S. aureus, producing up to 8 logs of reduction of MRSA infections when they are co-administrated. Such an anti-S. aureus synergy could be triggered with the currently used MB and amoxicillin clinical administration regimens. It is effective against S. aureus pathogens regardless of their antibiotic resistance backgrounds and does not create significant bacterial resistance with five days of continuous applications. It can lead to more than 99% of reduction of S. aureus infections established not only on the medical devices but also on the body surfaces.

CONCLUSIONS

Possessing a fusion of effectiveness, safety, sustainability, and broad applicability, this simple combination of light-activated MB and amoxicillin can ultimately reform our treatment against MDR S. aureus pathogens including MRSA, significantly alleviating the health and economic burden of S. aureus infections across the world.

A Cyclen-Functionalized Cobalt-Substituted Sandwich-Type Tungstoarsenate with Versatility in Removal of Methylene Blue and Anti-ROS-Sensitive Tumor Cells

Oxidative degradation by using reactive oxygen species (ROS) is an effective method to treat pollutants. The synthesis of artificial oxidase for the degradation of dyes is a hot spot in molecular science. In this study, a nanoscale sandwich-type polyoxometalate (POM) on the basis of a tetra-nuclear cobalt cluster and trivacant B-α-Keggin-type tungstoarsenate {[Co(C₈H₂₀N₄)]₄}{Co₄(H₂O)₂[HAsW₉O₃₄]₂}∙4H₂O (abbreviated as CAW, C₈H₂₀N₄ = cyclen) has been synthesized and structurally examined by infrared (IR) spectrum, ultraviolet–visible (UV–Vis) spectrum, X-ray photoelectron spectrum (XPS), single-crystal X-ray diffraction (SXRD), and bond valence sum (Σs) calculation. According to the structural analysis, the principal element of the CAW is derived from modifying sandwich-type polyanion {Co₄(H₂O)₂ [HAsW₉O₃₄]₂}^8– with four [Co(Cyclen)]²⁺, in which 1,4,7,10-tetraazacyclododecane (cyclen) is firstly applied to modify POM. It is also demonstrated that CAW is capable of efficiently catalyzing the production of ROS by the synergistic effects of POM fragments and Co–cyclen complexes. Moreover, CAW can interfere with the morphology and proliferation of sensitive cells by producing ROS and exhibits ability in specifically eliminating methylene blue (MB) dyes from the solution system by both adsorption and catalytic oxidation.

Improved Bladder Tumor RNA Isolation from Archived Tissues Using Methylene Blue for Normalization, Multiplex RNA Hybridization, Sequencing and Subtyping

Methylene blue (MB) is a dye used for histology with clinical importance and intercalates into nucleic acids. After MB staining of formalin fixed paraffin embedded (FFPE) muscle invasive bladder cancer (MIBC) and normal urothelium, specific regions could be microdissected. It is not known if MB influences RNA used for gene expression studies. Therefore, we analyzed MIBC using five different RNA isolation methods comparing patient matched FFPE and fresh frozen (FF) tissues pre-stained with or without MB. We demonstrate a positive impact of MB on RNA integrity with FF tissues using real time PCR with no interference of its chemical properties. FFPE tissues showed no improvement of RNA integrity, which we propose is due to formalin induced nucleotide crosslinks. Using direct multiplex RNA hybridization the best genes for normalization of MIBC and control tissues were identified from 34 reference genes. In addition, 5SrRNA and 5.8SrRNA were distinctive reference genes detecting <200 bp fragments important for mRNA analyses. Using these normalized RNAs from MB stained MIBC and applying multiplex RNA hybridization and mRNA sequencing, a minimal gene expression panel precisely identified luminal and basal MIBC tumor subtypes, important for diagnosis, prognosis and chemotherapy response.

Molecular Mechanisms of the Neuroprotective Effect of Methylene Blue

Methylene blue (MB) is the first fully synthetic compound that had found its way into medicine over 120 years ago as a treatment against malaria. MB has been approved for the treatment of methemoglobinemia, but there are premises for its repurposing as a neuroprotective agent based on the efficacy of this compound demonstrated in the models of Alzheimer's, Parkinson's, and Huntington's diseases, traumatic brain injury, amyotrophic lateral sclerosis, depressive disorders, etc. However, the goal of this review was not so much to focus on the therapeutic effects of MB in the treatment of various neurodegeneration diseases, but to delve into the mechanisms of direct or indirect effect of this drug on the signaling pathways. MB can act as an alternative electron carrier in the mitochondrial respiratory chain in the case of dysfunctional electron transport chain. It also displays the anti-inflammatory and anti-apoptotic effects, inhibits monoamine oxidase (MAO) and nitric oxide synthase (NOS), activates signaling pathways involved in the mitochondrial pool renewal (mitochondrial biogenesis and autophagy), and prevents aggregation of misfolded proteins. Comprehensive understanding of all aspects of direct and indirect influence of MB, and not just some of its effects, can help in further research of this compound, including its clinical applications.

Effects of toluidine blue O and methylene blue on growth and viability of pancreatic cancer cells

Amyloid precursor-like protein-2 (APLP2) and its C-terminal fragments (CTFs) are expressed at high levels in pancreatic cancer cells and knockdown of APLP2 expression inhibits tumor growth. CTFs are released from APLP2 by beta-secretase (BACE). In this study, our goal was to determine whether methylene blue (MethB) and toluidine blue O (TBO) could be used to slow down the growth and viability of pancreatic cancer cells (Hs 766T). We found that TBO and MethB decreased the growth and viability of Hs 766T cells in a dose- and time-dependent manner compared to vehicle-treated control, as demonstrated by MTT and trypan blue exclusion assays. Although TBO led to decreased expression of APLP2, MethB did not show any significant effect on APLP2. However, both MethB and TBO reduced BACE activity and the levels of APLP2 CTFs in Hs 766T cells. In conclusion, MethB and TBO may be valuable candidates for the treatment of pancreatic cancer by targeting APLP2 processing.

Evaluation of protective effects of methylene blue on cisplatin-induced nephrotoxicity

Cisplatin (CP) is used to treat various types of cancer. However, its usage is limited due to nephrotoxicity. This study aims to examine the applicability of methylene blue (MB) against CP-induced kidney injuries. In this study, twenty-eight male rats were divided into four groups. Following administration of a single dose of CP (5 mg/kg), animals received intraperitoneal injections (IP) of MB (4 mg/kg) for seven days. In the final phase of the experiment, serum was collected from rats, with blood urea nitrogen (BUN) and creatinine (Cr) levels measured. Hematoxylin-Eosin (H&E) and Masson's trichrome staining were performed to examine histological changes. Immuno-histological staining was used to evaluate caspase-3 protein expression. The results showed that the MB (4 mg/kg) + CP treated rats underwent a lesser weight loss compared to the CP group (p < 0.05 and p < 0.001, respectively). The kidney weight decreased significantly in the CP + MB group compared to the CP group (p < 0.05 and p < 001, respectively). BUN and Cr levels that were increased significantly in the serum of the CP group (p < 0.001) compared to the control group showed no significant increase in the MB + CP group compared to the control group (p = 0.842 and p = 0.989, respectively). There was a significant decrease in kidney tissue injuries in the CP + MB compared to the CP group (p < 0.001). The glomerular size was recovered in the CP + MB group compared to the CP (p < 0.05). The significant increase in the capsular space of the CP group compared to the control group (p < 0.001) was attenuated in the CP + MB. MB restored the histological alterations in the kidneys. Treatment with 4 mg/kg of MB reduced the expression levels of Caspase-3. In conclusion, this study provides evidence concerning the anti-apoptotic roles of MB in CP-induced kidney damage. In conclusion, MB has a positive impact on kidney function.

The Effects of Methylene Blue and Carbon Nanoparticles on Transplanted Lymph Node Survival, Reconstructed Lymphatic Function, and Changes in Inflammatory and Fibrosis Factors

BACKGROUND AND OBJECTIVES

Methylene blue (MB) and carbon nanoparticles (CNs) can be used as a simple method for reverse lymphatic mapping. We investigated whether the two tracers had an impact on the survival of lymph nodes and the function of reconstructed lymph vessels after transplantation, as well as the changes in surrounding related factors.

METHODS

The stained lymph nodes were non-vascularized transplanted into the contralateral popliteal fossa in mice. After 4 weeks, the lymphatic recanalization was detected. The samples were harvested for pathological detection and PCR. In addition, the transport ability of the recanalized lymphatics to tumor cells was also explored.

RESULTS

Compared with the control group, there was no significant difference of the MB and CNs groups in the drainage function of recanalized lymphatic vessels, the survival of lymph nodes, or the transport capacity to tumor cells. TNF-α and IL-6 were significantly higher in the two tracer groups (**p < 0.01). Besides, the α-SMA was significantly increased in the CNs group (*p < 0.05).

CONCLUSIONS

Two tracers have no effect on the survival of transplanted lymph nodes, nor do they affect the drainage ability or tumor cell capture ability of the reconstructed lymphatics, despite improving TNF-α and IL-6 levels and the deposition of CNs.

Effect of methylene blue on experimental postoperative adhesion: A systematic review and meta-analysis

Adhesion is a primary challenge following surgery, and the anti-adhesive effect of methylene blue (MB) has been investigated. This systematic review and meta-analysis aimed to evaluate the effect of MB on postoperative adhesions in experimental studies. We initially searched OVID-MEDLINE, EMBASE, and Google Scholar in February 2021, and then in May 2021. The anti-adhesive efficacy of MB was compared with that of the control (either placebo or nothing) after the surgical procedure. The primary and secondary outcomes were the macroscopic and microscopic adhesion scores, respectively. Traditional meta-analysis, meta-regression, and trial sequential analysis (TSA) were performed to analyze the retrieved outcomes. We included 13 experimental studies of 367 rats (200 rats received MB and 167 rats received placebo or nothing). The macroscopic adhesion scores were significantly lower in the MB-administered group than in the control group (standardized mean difference, 2.313; 95% confidence interval, 1.104 to3.523; I² = 94.0%, Tau = 2.059). Meta-regression analysis showed that macroscopic adhesion tended to decrease with an increase in MB dose. TSA demonstrated that the cumulative Z curve crossed both the conventional test and trial sequential monitoring boundary for the macroscopic adhesion score. MB had a beneficial effect on intraperitoneal adhesion following laparotomy, and adhesions decreased with increase in dose.

Evaluation of Spatially Targeted Scleral Stiffening on Neuroprotection in a Rat Model of Glaucoma

Purpose

Scleral stiffening may protect against glaucomatous retinal ganglion cell (RGC) loss or dysfunction associated with ocular hypertension. Here, we assess the potential neuroprotective effects of two treatments designed to stiffen either the entire posterior sclera or only the sclera adjacent to the peripapillary sclera in an experimental model of glaucoma.

Methods

Rat sclerae were stiffened in vivo using either genipin (crosslinking the entire posterior sclera) or a regionally selective photosensitizer, methylene blue (stiffening only the juxtaperipapillary region surrounding the optic nerve). Ocular hypertension was induced using magnetic microbeads delivered to the anterior chamber. Morphological and functional outcomes, including optic nerve axon count and appearance, retinal thickness measured by optical coherence tomography, optomotor response, and electroretinography traces, were assessed.

Results

Both local (juxtaperipapillary) and global (whole posterior) scleral stiffening treatments were successful at increasing scleral stiffness, but neither provided demonstrable neuroprotection in hypertensive eyes as assessed by RGC axon counts and appearance, optomotor response, or electroretinography. There was a weak indication that scleral crosslinking protected against retinal thinning as assessed by optical coherence tomography.

Conclusions

Scleral stiffening was not demonstrated to be neuroprotective in ocular hypertensive rats. We hypothesize that the absence of benefit may in part be due to RGC loss associated with the scleral stiffening agents themselves (mild in the case of genipin, and moderate in the case of methylene blue), negating any potential benefit of scleral stiffening.

Translational Relevance

The development of scleral stiffening as a neuroprotective treatment will require the identification of better tolerated stiffening protocols and further preclinical testing.

"Drug-Carrier" Synergy Therapy for Amyloid-β Clearance and Inhibition of Tau Phosphorylation via Biomimetic Lipid Nanocomposite Assembly

Amyloid-β (Aβ) toxicity is considered to be companioned by Tau phosphorylation in Alzheimer's disease (AD). The clinical AD therapy is usually subjected to low blood-brain barrier (BBB) penetration and complex interaction mechanisms between Aβ and phosphorylated Tau. A "Drug-Carrier" synergy therapy is herein designed to simultaneously target Aβ and Tau-associated pathways for AD treatment. To imitate natural nanoparticle configuration, the endogenous apolipoprotein A-I and its mimicking peptide 4F fused angiopep-2 (Ang) are sequentially grafted onto lipid nanocomposite (APLN), providing liberty of BBB crossing and microglia targeted Aβ clearance. For synergy treatment, methylene blue (MB) is further assembled into APLN (APLN/MB) for Tau aggregation inhibition. After intravenous administration, the optimized density (5 wt%) of Ang ligands dramatically enhances APLN/MB intracerebral shuttling and accumulation, which is 2.15-fold higher than that Ang absent-modification. The site-specific release of MB collaborates APLN to promote Aβ capture for microglia endocytosis clearance and reduce p-Tau level by 25.31% in AD pathogenesis. In AD-Aβ-Tau bearing mouse models, APLN/MB can relieve AD symptoms, rescue neuron viability and cognitive functions. Collectively, it is confirmed that "Drug-Carrier" synergy therapy of APLN/MB is a promising approach in the development of AD treatments.

Photodynamic Methylene Blue-Embedded Intragastric Satiety-Inducing Device to Treat Obesity

Bariatric surgery is the most effective treatment for weight recidivism, and endoscopic bariatric treatment has been developed for a similar effect without anatomical modification. An intragastric satiety-inducing device (ISD) is a minimally invasive approach to induce satiety by continuously pressing the stomach and stimulating ghrelin-producing cells. To enhance the therapeutic effects of ISD, photodynamic therapy (PDT) can be combined by generating singlet oxygen under laser irradiation. Methylene blue (MB), as a photosensitizer (PS), was coated on the ISD surface for singlet oxygen production to stimulate or destroy cells. Ghrelin-producing cells effectively inhibited ghrelin secretion and induced gastrointestinal satiety signals compared with the MB-uncoated device via PDT. Herein, MB-embedded ISDs were developed, and their photoresponsive abilities were demonstrated in the device itself and in vitro. PDT with an MB-embedded ISD was successfully performed in a porcine model, which had 2-fold reduced body weight gain (12% in PDT vs 24% in control) and 2-fold reduced ghrelin levels (21.2 pg/mL in PDT vs 45.1 pg/mL in control) at the first week postprocedure. The simple and unique operation extends the point of view in PDT and is expected to be a novel endoscopic bariatric therapy.

Effects of methylene blue on microcirculatory alterations following cardiac surgery: A prospective cohort study

BACKGROUND

Methylene blue is used as rescue therapy to treat catecholamine-refractory vasoplegic syndrome after cardiac surgery. However, its microcirculatory effects remain poorly documented.

OBJECTIVE

We aimed to study microcirculatory abnormalities in refractory vasoplegic syndrome following cardiac surgery with cardiopulmonary bypass and assess the effects of methylene blue.

DESIGN

A prospective open-label cohort study.

SETTING

20-Bed ICU of a tertiary care hospital.

PATIENTS

25 Adult patients receiving 1.5 mg kg-1 of methylene blue intravenously for refractory vasoplegic syndrome (defined as norepinephrine requirement more than 0.5 μg kg-1 min-1) to maintain mean arterial pressure (MAP) more than 65 mmHg and cardiac index (CI) more than 2.0 l min-1 m-2.

MAIN OUTCOME MEASURES

Complete haemodynamic set of measurements at baseline and 1 h after the administration of methylene blue. Sublingual microcirculation was investigated by sidestream dark field imaging to obtain microvascular flow index (MFI), total vessel density, perfused vessel density and heterogeneity index. Microvascular reactivity was assessed by peripheral near-infrared (IR) spectroscopy combined with a vascular occlusion test. We also performed a standardised measurement of capillary refill time.

RESULTS

Despite normalised CI (2.6 [2.0 to 3.8] l min-1 m-2) and MAP (66 [55 to 76] mmHg), patients with refractory vasoplegic syndrome showed severe microcirculatory alterations (MFI < 2.6). After methylene blue infusion, MFI significantly increased from 2.0 [0.1 to 2.5] to 2.2 [0.2 to 2.8] (P = 0.008), as did total vessel density from 13.5 [8.3 to 18.5] to 14.9 [10.1 to 14.7] mm mm-2 (P = 0.02) and perfused vessel density density from 7.4 [0.1 to 11.5] to 9.1 [0 to 20.1] mm mm-2 (P = 0.02), but with wide individual variation. Microvascular reactivity assessed by tissue oxygen resaturation speed also increased from 0.5 [0.1 to 1.8] to 0.7 [0.1 to 2.7]% s-1 (P = 0.002). Capillary refill time remained unchanged throughout the study.

CONCLUSION

In refractory vasoplegic syndrome following cardiac surgery, we found microcirculatory alterations despite normalised CI and MAP. The administration of methylene blue could improve microvascular perfusion and reactivity, and partially restore the loss of haemodynamic coherence.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04250389.

Methylene blue in management of COVID19

Many novel drugs were used in COVID19 pandemic to improve outcome. One such molecule is Methylene blue which is a, tricyclic phenothiazine compound approved for the treatment of acquired methemoglobinemia and some other uses US FDA. This molecule was found to inhibit the interaction of COVID19 virus and target cells in dose dependent manner. It was also found to inhibit interaction of viron with host cells, by inhibiting interaction of SARS CoV2 spike protein and ACE inhibitor receptor interactions.

MATERIAL AND METHODS

A) Aim &amp; Objectives: To evaluate the effect of Nebulised Methylene blue on the clinical course and outcomes of patients with COVID-19 infections. B) Study design Observational Study C) Participants 63 COVID19 RT-PCR positive cases divided in 3 groups. Group 1 consists of patients who were prescribed Methylene blue nebulization in form of Methylene blue 0.5 mg via nebulization along with bronchodilator Levosalbutamol (1.25 mg) + Ipratropium (500 mcg) three times a day . Group 2 consists of patients with Methylene blue nebulization in form of Methylene blue 0.5 mg via nebulization along with inhalational steroid Budesonide (1 mg). Group 3 acted were those patients who had no Methylene blue nebulisation in their treatment.

OBSERVATION

1) Analysis 63 cases were divided in 3 groups of 21 each, descriptive and frequency analysis of cases in groups are shown.

CONCLUSION

No statistically significant difference in outcome measures like Spo2, duration of hospital stay or inflammatory markers. A general trend of fall in inflammatory markers and O2 requirements in group receiving methylene blue but this difference was not consistantly statistically significant.

Methylene Blue-Mediated Antimicrobial ​Photodynamic Therapy Against Clinical Isolates of Extensively Drug Resistant ​Gram-Negative Bacteria Causing Nosocomial Infections in Thailand, An In Vitro Study

BACKGROUND/PURPOSE

Some multidrug-resistant gram-negative bacteria as a global threat have been recently prioritized for research and development of new treatments. We studied the efficacy of methylene blue-mediated antimicrobial photodynamic therapy (MB-aPDT) for the reduction of extensively drug-resistant Acinetobacter baumannii (XDR-AB) and Pseudomonas aeruginosa (XDR-PS) and multidrug-resistant Klebsiella pneumoniae (MDR-KP) isolated in a university hospital setting in Thailand.

METHOD

Two isolates of each selected bacterium were collected, XDR-AB1 and AB2, XDR- PS1 and PS2, and MDR-KP1 and KP2. Three triplicate experiments using various MB concentrations alone, various red light fluences alone, as well as the selected non-toxic doses of MB and fluences of red light combined as MB-aPDT were applied on each selected isolate. The colonies were counted [colony forming units (CFU)/ml]. Estimation of the lethal treatment dose defined as reduction of > 2 log₁₀ in CFU/ml compared with untreated bacteria.

RESULT

There were generally negligible changes in the viable counts of the bacterial suspensions treated with all the MB concentrations (p > 0.05). In the second experiment with the only red light treatments, at fluences higher than 2 J/cm, reduction trend in viable counts across all the isolates was observed. Only for MDR-KP1, however, the lethal dose was achieved with the highest fluence of red light (80 J/cm). With the concentration of MB, 50 and 150 mg/L in the third experiment (MB-aPDT), the greater bacterial reduction was observed in all clinical isolates leading to their lethal viable cell reduction when escalating the light fluence to 80 J/cm.

CONCLUSIONS

MB-aPDT evidently killed the selected XDR and MDR-gram negative bacteria. In highly drug-resistant crisis era, MB-aPDT could be a promising option, particularly for local infections and infection complicating chronic wounds.

Depth distributions of bacteria for the Pseudomonas aeruginosa-infected burn wounds treated by methylene blue-mediated photodynamic therapy in rats: effects of additives to photosensitizer

SIGNIFICANCE

Pseudomonas(P.) aeruginosa, a common cause of infection in burns, acquires antibiotic resistance easily and forms biofilms efficiently. Thus, it is difficult to control P. aeruginosa infection in burn wounds, which causes lethal septicemia. Antimicrobial photodynamic therapy (aPDT) is attractive as a new strategy to treat burn wound infections with drug-resistant bacteria.

AIM

We examined the efficacy of methylene blue (MB)-mediated aPDT with various additives in a tissue depth-resolved manner to find conditions that minimize the bacterial invasion.

APPROACH

We applied MB-mediated aPDT with LED array illumination to an extensive, full-thickness burn infected with P. aeruginosa in rats for three consecutive days (days 0, 1, and 2). On day 2, the depth distributions of bacteria were assessed based on the histological analysis using Gram staining. We examined how the addition of ethylenediaminetetraacetic acid (EDTA), ethanol, and dimethyl sulfoxide (DMSO) affected the efficacy of aPDT.

RESULTS

Pure MB-mediated aPDT significantly reduced the numbers of bacteria with biofilms on the wound surface and in the epidermis compared with those for the control tissue (saline only). However, there were many bacteria in the deeper region of the tissue. In contrast, MB/EDTA/ethanol/DMSO-mediated aPDT minimized the numbers of bacteria in the broad depth region of the tissue. Still, a limited number of bacteria was observed in the subcutaneous tissue.

CONCLUSIONS

The depthwise analysis of bacteria demonstrated the efficacy of the MB-mediated aPDT with the addition of EDTA, ethanol, and DMSO in controlling burn wound infections. However, further improvement of the therapy is needed to suppress bacterial migration into the deep tissue completely.

The Potentials of Methylene Blue as an Anti-Aging Drug

Methylene blue (MB), as the first fully man-made medicine, has a wide range of clinical applications. Apart from its well-known applications in surgical staining, malaria, and methemoglobinemia, the anti-oxidative properties of MB recently brought new attention to this century-old drug. Mitochondrial dysfunction has been observed in systematic aging that affects many different tissues, including the brain and skin. This leads to increaseding oxidative stress and results in downstream phenotypes under age-related conditions. MB can bypass Complex I/III activity in mitochondria and diminish oxidative stress to some degree. This review summarizes the recent studies on the applications of MB in treating age-related conditions, including neurodegeneration, memory loss, skin aging, and a premature aging disease, progeria.